Now that the weather is nice outside, I love to grill a bunch of chicken breasts or pork chops and vegetables, and eat it different ways for a few days -- in a sandwich, on a salad, with sides.
A crockpot of pulled chicken or pork, or a brisket with rolls and sides is another thing that will last a while.
Blender gazpacho is another food that's easy to make in bulk, but I do that in the summer.